Field of the Invention
Embodiments of the present invention generally relate to a method and apparatus for touch sensing, and more specifically, a capacitive touch sensing device having grid electrodes for improved absolute sensing, and methods for using the same.
Description of the Related Art
Input devices including proximity sensor devices (also commonly called touchpads or touch sensor devices) are widely used in a variety of electronic systems. A proximity sensor device typically includes a sensing region, often demarked by a surface, in which the proximity sensor device determines the presence, location and/or motion of one or more input objects. Proximity sensor devices may be used to provide interfaces for the electronic system. For example, proximity sensor devices are often used as input devices for larger computing systems (such as opaque touchpads integrated in, or peripheral to, notebook or desktop computers). Proximity sensor devices are also often used in smaller computing systems (such as touch screens integrated in cellular phones).
Many proximity sensor devices utilize an array of sensor electrodes to measure a change in capacitance indicative of the presence of an input object, such as a finger or stylus, proximate the sensor electrodes. The conductive routing traces utilized to couple the array of sensor electrodes to a processing system typically are arranged in a layer disposed between the sensor electrodes and a conductive housing of the sensor device. Since the film stack may deflect or bend when exposed to an input force such as a touch event, the conductive routing traces may be displaced towards the housing. The resulting change in distance between the conductive routing traces and the housing causes a change in the background capacitance, which produces a distortion in an image of measured response from the sensor device. The distortion degrades the performance of the sensor device.
Thus, there is a need for an improved proximity sensor device.